Note: Only ASME can make code interpretations.
More than a decade ago the then head review engineer of a jurisdiction first told me that 44w was allowed in pressure vessels, pointing out the line in the IID code book showing CSA G20.41 38W. Today a field inspector for the same jurisdiction is insisting that 44w is not acceptable for use in pressure boundaries on ASME VIII-1 pressure vessels. This memo is about a small vessel that was accidently made out of 44w materials.
44w steel is a Canadian steel grade specified in CSA-G40.21. The specification has a wide variety of grades available in plate and structural forms. The use of 44w (or 50w or other CSA G20.41 grades) has not been an issue for welded structural supports used on pressure vessels.
ASME IID lists 38w as SA/CSA-G40.21 38W (page 14 of the 2008 update) - tensile strength of 60,000 psi, 38,000 psi yield. The allowable stress at ambient is 17,100 psi, maximum temperature is 650°F.
ASME IID lists SA-36 (page 10 of the 2008 update) - tensile strength of 58,000 psi, 38,500 psi yield. The allowable stress at ambient is 16,600 psi, maximum temperature is 650°F. This is a similar but not identical material to 44w.
ASME IID does not list 44w.
38w is not practically available in Canada. 44w is common. The steel mill that made the 44w plates for this vessel had not heard of 38w before.
ASME IX lists 38w and 44w both as P 1 Gr 1 materials (page 109).
Both 38w and 44w are specified in CSA G20.41 spec. (numbers below are simplified, see the full CSA G20.41 spec for more detailed requirements).
|38w||0.20% max||38 ksi min||60 ksi min||18%|
|44w||0.22% max||44 ksi min||65 ksi min||18%|
|44w MTR||0.17%||59 ksi||73.5 ksi||30%|
Note that the vessel MTR shown above could have been triple certified by the mill as 38w/44w/50w, and if that had been done (38w showing), would be acceptable for use on this pressure vessel.
38w and 44w are both listed in ASME section IV Table HF-300.1 "SA/CSA-G40.21 as specified in Section IIA grade 38W or 44W, may be used in lieu of SA-36 for plates and bars not exceeding 3/4 in. (20mm). For use at the same allowable stress values as SA-36." (page 76, 2007 edition).
The steel used from the material test report listed above was recertified by the mill as 38w/44w/50w making it a listed material. See ASME VIII-1 UG-10(a)(1).
If requested, Pressure Vessel Engineering will design pressure vessels using 44w for pressure boundaries. The drawings and calculations will state 38w and material strength allowables for 38w will be used. Be careful to review mtrs before purchasing materials to ensure that the material can be recertified by the mill under 38w. Use of other explicitly code listed materials is recommended.
The use of 44w or 50w for structural supports is currently not a problem and is common practice in Canada.
We have asked ASME to list 44w and 50w in IID to eliminate the unnecessary expense of recertifying materials. As of Oct 2010, 44w is being considered for addition to the IID code listings, probably at stress levels currently allowed for 38w. 50W would require material testing and is not currently being considered.